November 27, 2009Comments Off on The Mantellas – Madagascar’s Answer to the Dendrobatids (Poison Frogs)2456 Views

Madagascar’s Mantellas or Golden Frogs (Family Mantellidae) are, in many ways, the ecological equivalents of Latin America’s Poison Frogs (Family Dendrobatidae), and illustrate nicely the concept of convergent evolution – unrelated animals from different parts of the world that have developed similar adaptations. Although less commonly kept than the poison frogs, these tiny, brilliantly-colored gems are gaining in popularity. Following is a brief overview of the group.

Range and Diversity

Mantellas are found only on Madagascar, off the southeast coast of Africa, and are unique enough to warrant their own family, Mantellidae. Sixteen species have been described thus far, but that number will almost certainly increase as the group is studied more closely. Nearly all are exceptionally colorful – more so than the better known Poison Frogs (Dendrobates spp.) in many cases.

Similarities to Poison Frogs

Both Mantellas and Poison Frogs are small, brightly-colored, diurnal (active by day), and usually make little attempt to conceal themselves. All forage on land or in trees, are protected by virulent skin toxins, exhibit complex breeding behaviors, and lay eggs in on land.

Mantella reproductive strategies roughly follow those of the Poison Frogs. Males call during the day from exposed sites on land – light markings on the vocal sacs may serve as a visual stimulus to females. They wrestle for dominance, with the loser being flipped onto his back but otherwise unharmed. Ten to thirty eggs, which are fertilized externally, are deposited in nests below leaf litter.

Tadpole development has been little studied; those which have been researched hatch in 2-7 days and wriggle or are washed by rain to temporary pools and brooks. They feed upon algae and decaying plants and animals, and transform into frogs in 6-8 weeks. Sexual maturity is attained in 12-14 months.

Mantellas in the Terrarium

Mantellas may be kept in much the same manner as most poison frogs but, being even smaller, they are a bit harder to feed. A source of springtails, fruit flies and pinhead crickets is a must.

Despite their diminutive statures, Mantellas are efficient predators with quite large appetites – a 1.8 inch long Bronze Mantella (Mantella betsilio) was observed to consume 53 ants in just 30 minutes!

Further Reading

A review of the status of the various mantellas and the CITES proposal for their protection is posted here.

In 1705, a painting of a Pink-toed Tarantula consuming a hummingbird, published in Maria S. Merian’s book on the insects of Suriname, aroused so much attention (and horror!) that all New World tarantulas are commonly termed “bird-eating spiders” to this day. It seems now that amphibian fanciers have their own dramatic bird-eater – Limnonectes megastomias, an aquatic frog recently described from 3 locations in Thailand.

An Aquatic Ambush Predator

The newly discovered frog is largely aquatic, and apparently catches birds that come to the water’s edge to drink – quite a unique feeding strategy for a frog (I once saw a surprising film of African Side-necked Turtles catching doves in this manner).

It is assisted in hunting by large (to 2 inch) “fangs” and a head that is disproportionately large for the body. The fangs are not true teeth but rather extensions of the jawbone, known as odontoid processes. The African Bullfrog and the South American Horned Frogs, known also for consuming vertebrates (and biting the hand that feeds them!), also sport odontoid processes. Insects and other frogs have also been recorded as prey.

Same Bodies, Larger Heads – Sexual Dimorphism

Interestingly, the heads and “teeth” of male Bird-eating Frogs grow much larger than those of females, despite similar body sizes. In certain other creatures (i.e. Barbour’s Map Turtles) this strategy allows the sexes to consume different diets and, it is theorized, avoid competition. Researchers also believe that the enlarged teeth are used in combat, as many males carry scars.

So Much to Discover

There are over 50 species classified in the genus Limnonectes- the new “bird-eater” appears most closely related to the Kuhl’s or Large-Headed Frog, L. Kuhlii, but little is known of its natural history (the photo attached is of a Kuhl’s frog).

This new species was first observed at the Sakaerat Environmental Research Station, an area that has been extensively studied for 40 years. The fact that such a large and unique frog was able to remain undiscovered in this area illustrates the untold opportunities open to those who wish to get out and look around in just about any habitat – recently a new centipede was discovered in NYC’s Central Park!

Further Reading

Another toothed amphibian behemoth, the African Bullfrog, also takes quite large prey…to read about a most unusual frog meal, please see my article An Appetite for Cobras.

Limnonectes kuhlii image referenced from wikipedia and originally posted by W. Djatmiko

Many amphibian websites tend to focus only on popularly kept species. Today I’ve compiled a list that addresses both common species and less well-known topics, such as amphibian health care and caecilian husbandry.

Salamanders and Newts

This is the most comprehensive salamander-oriented website available. I’m very impressed by the depth of interest and expertise evidenced by many of the members, who are always eager to help less-experienced hobbyists. The forum discussions are always interesting and often break new ground, and the posted articles and care sheets are top notch.

Frogs and Toads

This informative website focuses on frogs other than the “attention-grabbing” poison frogs, although discussions concerning these are welcome. It’s very refreshing to see that North American frogs and other under-represented groups are given the spotlight here. Popular pet trade species such as White’s treefrogs, horned frogs and African bullfrogs, are also well covered.

The discussion forums show great promise, and the care sheets and natural history information supplied are of excellent quality.

I’ve never understood why toads have always been given so little attention by amphibian enthusiasts. They exhibit an amazing diversity of forms and lifestyles and, on the whole, make much hardier and more responsive pets than do frogs. The folks at ToadilyToads have taken great strides in remedying this unfortunate situation.

This website deals with all aspects of toad keeping and conservation, and provides some enjoyable activities as well. I was especially happy to see that a good deal of attention is given to encouraging local species through backyard and similar habitat improvements.

This site is a great resource for those who keep or are interested in learning more about the ever-popular poison frogs and their relatives (“dart frogs”, Mantella spp., Dendrobates spp., etc.). The discussion forums are quite active, and quality care and natural history information is available.

Caecilians

Gymnophiona.org

A real find for those interested in this little-studied but fascinating amphibian order, this site posts some of the most well-researched caecilian natural history information available. The captive care details provided are a rare and valuable resource.

Those interested in caecilian husbandry are well-situated to uncover volumes of new information on these unusual creatures; this website would serve well as a vehicle to publish such and to interact with others working with caecilians.

Health Care

I’ve long relied upon Dr. Kevin Wright, founder of the Arizona Exotic Animal Hospital, for answers to my most difficult pet and zoo animal health and husbandry questions.

One of the world’s foremost exotic animal veterinarians and coauthor of the classic Amphibian Medicine and Captive Husbandry, Dr. Wright has posted a variety of much-needed amphibian care sheets on the hospital’s website. Covering topics ranging from general emergencies to parasites, the information contained therein is an invaluable resource to the amphibian keeper. Hobbyists whose interests extend beyond amphibians will find a wealth of information on the care of invertebrates, fishes, reptiles, birds and mammals as well…a real treasure trove! For information on phone and email consultations with Dr. Wright, please click here.

Conservation

Amphibian Ark

Amphibian Ark was formed in response to the wave of amphibian extinctions occurring worldwide. The organization coordinates both field and captive-management conservation programs in association with zoos, museums and researchers worldwide.

The Amphibian Ark Newsletter, posted monthly, is the internet’s most comprehensive collection of articles dealing with amphibian research, conservation and natural history.

October 7, 2009Comments Off on The Unique, Endangered Panamanian Golden Frog or Harlequin Toad – Part 23028 Views

Please see Part I of this article to learn about the natural history of the Panamanian Golden Frog , Atelopus zeteki, including it’s unique mode of communication.

Status of Wild Populations

Panamanian Golden Frog numbers are plummeting, most likely due to an epidemic of the largely incurable fungal infection
Chitridiomycosis. The fungus responsible, Batrachochytrium dendrobatidis, has been implicated in the declines and extinctions of numerous amphibian species worldwide. This frog is also threatened by deforestation, stream siltation, pollution and collection for use as a promotional tool in Panama’s restaurant, hotel and tourism industries (this practice is illegal, but enforcement is often lax).

It is estimated that Golden Frog populations have declined by 80% in both numbers and extent of occurrence over a 10 year period. At least 2 distinct populations are extinct, with 1 such extinction occurring within the span of several months. Golden Frogs are designated as “Critically Endangered” by the IUCN and listed on Appendix I of CITES. They are legally protected by Panama and the subject of a cooperative rescue program, administered by the USA and the Republic of Panama, known as “Project Golden Frog”. Fortunately, the Golden Frog breeds well in captivity.

Unique Skin Toxins

This frog’s skin contains extremely virulent nerve toxins that differ from those produced by other amphibians. Known as “zetekitoxins”, the poison contained in the skin of a single 2-inch-long frog is sufficient to kill 1,200 mice! It is believed that these toxins are produced in association with symbiotic bacteria, but this has not yet been definitively documented.

Cultural Significance

The Panamanian Golden Frog is the national animal of the Republic of Panama, and has traditionally been associated with matters relating to good fortune. Pre-Columbian indigenous people molded its likeness in gold and clay talismans known as “huaces”.

In the late 1980’s I was privileged to breed the now rarely-seen Smoky Jungle Frog, Leptodactylus pentadactylus, a large (8 inch snout-vent length) Latin American native that constructs foam nests on land. In the wild, rain washes the tadpoles into a nearby pool, where they develop in normal frog fashion…following suit, I successfully reared a number in water. I subsequently learned that some frog nests are placed far from the water’s edge, and that the tadpoles therein develop entirely on land. But what did they eat…the nest’s foam, perhaps? There were theories, but no answers.

Subterranean Frog Nests

Herpetologists working with the closely related Mountain Chicken Frog (L. fallax) at the Durrell Wildlife Conservation Trust have recently solved the riddle – and captured the bizarre event on film. Mountain Chicken Frogs, highly endangered and limited to Dominica, St. Kits, Martinique and a few neighboring islands, lay their eggs in foam nests underground, and the tadpoles develop without ever seeing water.

The startling footage taken by the researchers, shows scores of tadpoles gorging on unfertilized eggs produced by their mother. In sharp contrast to certain more “civilized” oophagus (egg-eating) poison frog tadpoles, the chicken frog larvae do not wait until the eggs are actually deposited, but rather swarm about the female’s cloaca, eating ravenously as the eggs emerge. It’s quite a scene!

A Taxing Time for Mom

Subsequent research has revealed that the harried mother uses her rear legs in an attempt to re-distribute the unusual food, and perhaps to give all of her gluttonous progeny a chance to feed. She has her work cut out for her…the 25 to 50 tadpoles that she rears require 10,000 to 25,000 unfertilized eggs to see them through to metamorphosis!

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